8-bit Dynamic Element Matching based Feedback Controller Applied to an Instrumentation Amplifier

Abstract

The instrumentation amplifier, which incorporates Dynamic Element Matching (DEM) and a resistive network, utilizes a digital controller to reduce gain error by means of averaging. This paper assesses the feasibility of combining, within a general-purpose microcontroller, the appealing DEM, i.e., very accurate resistive ratios ranging between 1 and 15, with the associated versatile and scalable interrupt-aware digital controller. Given a mixedsignal system, a hybrid evaluation environment has been developed to perform relevant testbenches for assessing the systems performance, i.e., DEM controller, muxes, OpAmps, with respect to relevant metrics for integrated digital and mixed-signal circuits, i.e., energy, delay, footprint, precision. When implementing our design in a commercial 180nm technology, the gain precision of a typical amplifier is improved by more than 1800 times, with the error converging to as low as 10s of ppm, for Gaussian mismatch distribution between-1% and 1% with the cost of DEM digital circuitry which adds about 30000 µm² of chip area and will consume 194 µA.